SMPS What is a switched-mode power supply?
Switched-mode power supplies are electronic supplies that incorporate switching regulators to convert electrical power efficiently. They are widely used in a range of modern applications thanks to characteristics like efficiency, low cost, and adaptability.
A switched-mode power supply, sometimes known as a switch-mode power supply or ‘SMPS’, is an electronic power supply that integrates a switching regulator for efficient electrical power conversion. Like other supplies, an SMPS transfers power from a DC or AC source to DC loads while converting voltage and current.
Unlike in linear power supplies, the pass transistor of a switched-mode supply is constantly switching between low-dissipation, full-on, and full-off states. It spends very little time in high dissipation transitions, and this minimizes the amount of electricity that is wasted.
Basic concept of a switch-mode power supply
The core concept of a SMPS is that regulation is handled by using a switching regulator. This uses a series switching element that turns the current supply to a smoothing capacitor between on and off states. The time that the series element is turned on for is controlled by the voltage on the capacitor. If the voltage is higher than what’s needed, the switching element is turned off. If lower than required, it’s turned on.
In its most basic form, the operation of a SMPS involves unregulated input DC being fed to the inverter section which consists of fast-switching components such as MOSFETs and bipolar transistors. This leads to the input voltage to appear at the primary winding as pulses at 20 to 200 kHz switching frequency. The transformer output is then rectified and smoothed to produce the required DC voltages.